Contact-pin for connecting-plugs and process for the manufacture thereof



0. STALHANE AND 6. 0. KRING. CONTACT PIN FOR C ONNECTING HUGS AND PROCESS FOR THE MANUFACTURE THEREOF.

' APPLICATION FILED JULY 1919.

Patented May 3, 1921.

WWW WM UNITED STATES I PATENT OFFICE.

OTTO STALHANE AND OLOF OSKAR KRING, 0F DJU'RSHOLM, SWEDEN.

CONTACT-PIN FOR CONNECTING-PLUGS AND PROCESS FOR THE MANUFACTURE THEREOF. i

Specification of Letters Patent.

Patented May 3, 1921.

Application filed .l'uly' 8, 1919. Serial No. 309,441.

To all whom it may concern:

Be it known that we, OTTO OLOF OSKAR KRING, subjects of the Kin of Sweden, residing in Djursholm, in the Kingdom of Sweden, have invented certain new and useful Improvements in Contact-Pins for Connecting-Plugs and"Processes for the Manufacture Thereof, of which the following is a specification.

In connecting plugs of previously known constructions, the contact pins have either been made in the form of solid metal cylinders, or of hollow nonelastic cylinders, pressed out of plates.

In the former case it is usual to split the front part of the pin with one or more cuts, in order to obtain a somewhat elastic contact between the pin and the sleeve in the socket. This construction, however, is attended by considerable drawbacks. In the first place' it is comparatively expensive, partly owing to the elaborate treatment required, partly because far too largea part of the. material has to be scrapped. Moreover, a contact manufactured in this manner afiords an unsatisfactory contact between the sleeve ,and the pin, owing to the fact that the cross section of the two halves of the split contact pin, viz., the complete semi-circle is, from the point of view of flexibility, a by no means suitable section. It is true that a certain elasticity can be attained by the use of a very hard material,

- but from a manufacturing point of view,

this entails far too serious drawbacks. The

result is, as is known, that the connecting plugs now employed do not work satisfactorily, inasmuch as they soon get-damage by the formation of an electric arc owing to unsatisfactory contact between sleeve and pin. A contact pin pressed out of plate is, from a manufacturing point of view, much more reliable than one constructed in accordanoe with the above-mentioned process; but as the previously employed pins made of plate are pressed in one piece, without any possibility of acquiring elacticity, they necessitate the use of elastic contact sleeves, which as a'rule, are not used in practice.

The present invention relates to a contact pin of such a construction that all the abovementioned drawbacks are practically eliminated. In accordance with the present invention, the contact pin is so constructed that it can be manufactured by stamping or y pressing out of metal plate, in such a manner STALHANE and vention. Fig. 3 shows an end view of the same pin. .Fig. 4 shows'a s amped-out blank for such a pin.

For the purpose of the. manufacture of the contact pin, there is first stamped out of plate a blank of approximately the shape indicated in Fig. 4, furnished with three fingers 1, which by pressing have been given a crescent-shaped cross section. .These fingers, afterhaving been pressed together into the finished shape shown in Figs. 1-3, form the forward elastic or yielding'part of the pin. Partly owing to the crescent-shaped section obtained in the pressing, these fingers acquire a high degree'of elasticity, which it 1s impossible to obtain in pins turned out of metal rods. In the turned pins, moreover, traces or grooves from the lathe steel are always left on the cylindrical grooves so that a certain roughness is felt when the pin is inserted into the sleeve. These ridges it is true, are soon worn down, but then they cause the diameter of the pin to be so diminished that bad contact arises, resulting in the formation of an electric arc. The flap 2 is intended to be bent along the dotted line 3, so that the threaded holes 4 and 5 will lie opposite to one another. Next, the flap 6 is bent over, so that the hole 7 will come opposite the holes 4-5, but in such a way that a space is left between the flaps 6 and the bent-over or folded flap 2. By reason of this formation, a double ad vantage is obtained, namely, first, that suflisurface in the form of ridges between the cient material (the double thickness of tightening of the screw 8, the conductor,

which is to be connected to the pin is jammed between the bent flaps 2 and 6 in a very advantageous manner. In order to facilitate the insertion of the pin in the sleeve, the

tips of the fingers 1 should, when the blank is being pressed together, he fashioned in such a way, that they together form a rounded end 9 of the pin, as shown in Figs. 1 and 2. As is' apparent from Fig. 4, a comparatively insignificant amount of the material is wasted as scrap in stamping the blank out of the plate, but, even including this scrap, less material is consumed than is contained in a finished pin of the previous construction.

The form of the contact pin shown in the drawing is to be regarded merely as anillustrative example; the pin may conceivably be made or manufactured in other ways, while retaining the characteristic features of the invention. Thus the contact pin may conceivably be made with a different number of slits, or a different number (two or more) of fingers or tongues than that shown in the drawing; or also the flap 2 may be omitted, or the flap 6 may be made in another way than that described by way of example.

Having thus described our invention, we declare, that what we claim is Contact pins for electrical connecting plugs, made of metal plate, the part of the pin Which is intended to be inserted into'the contact socket being divided by longitudinal slits in its longitudinal direction into a number of fingerlike parts integral with each other and essentially of a crescentshaped cross section, so that the pin will obtain substantially a cylindrical form with a high degree of elasticity in a radial direction.

In witness whereof we have hereunto set our hands in presence of two witnesses.

OTTO STALHANE. ()LOF OSKAR KRING.

Witnesses:

AUG. HAGELIN, ALMA Pnrcrnnson. 

